The present invention relates to a device and method for improving the stability of a boat.
With many small boats, i.e. those with a waterline length of less than seven meters, problems are encountered with providing adequate stability to shallow draft hulls and adequate buoyancy in case the hull becomes filled with water, e.g. by capsizing or being holed. Often buoyancy is provided by internal airtight tanks or compartments. However, these occupy valuable space within the hull. It has also been proposed to form an integral buoyancy collar around the gunwale of the hull during manufacture to provide external buoyancy to the hull. However, this method is expensive and can only be applied to boats during manufacture. The large number of existing hulls can not be given this form of buoyancy.
It has been proposed to provide inflatable fenders around the hull. These can also act as buoyancy aids, but only over comparatively short lengths of the hull. Moreover, these fenders are merely suspended over the side of the boat and will therefore provide buoyancy only when the hull is partially sunk.
It has been proposed to fix a longitudinal buoyancy collar along the hull of the boat at a number of points, see U.S. Pat. No. 3,797,435. However, such a collar will drag in the water (see FIG. 3 of the U.S. patent) and will affect the handling of the boat on which it is mounted, unless it is provided with upper fixings as shown in FIG. 5 of the U.S. patent. This increases the cost of mounting the collar and, since the up-thrust of the collar is applied only at the fixings, will impose localised stresses on the hull. Also at least part of the up-thrust of the collar is applied through the lower mountings which are below the centre of gravity of the hull and will tend to exert a capsising effect on the hull, especially in cross seas.
It has also been proposed to fit an envelope around the hull of a boat to cover holes in the hull or to protect the hull. Whilst such envelopes may have an inflatable collar as an integral part thereof, that collar does not grip the hull and remains in position on the hull solely because of the envelope which encases the hull. Such envelopes are cumbersome in use and are not capable of being fitted to a wide variety of hulls.